with two columns on the outside and two pilasters within, as will be mentioned hereafter, and between these the whole space is left for the windows which are to give light to the Cupola.
On the side looking towards the centre of the Cupola these great piers present a surface of thirty-six palms, but on the other side of nineteen and a half palms only,[1] each has two columns on the exterior side, the dado at the foot of these measuring eight palms and three quarters, and eight and a half palms in height; the base is five palms eight inches broad, and. . . . palms eleven inches high; the shaft of the columns has forty-three and a half palms in height; the diameter is five palms six inches at the base, and above four palms nine inches: the Corinthian capital is six and a half palms high, or with the mouldings nine palms. Three quarters only of these columns are seen, the fourth being let into the corner, but in the centre there projects a pilaster, which forms an acute angle; between the pilasters is an entrance forming an arched doorway, five palms broad and thirteen palms five inches high, but above this level it is filled in with solid masonry even to the capitals of the columns and pilasters, being united with two other pilasters similar to those which form the acute angle beside the columns, and these decorate the sides of the sixteen windows constructed around the circle of the tribune, each window having a clear light twelve and a half palms wide, and about twenty-two palms high.
The windows are adorned on the outside by an architrave of varied character two palms and three quarters broad, and on the outside they are in like manner decorated with a similarly varied range of pediments and arches intermingled, being broader without and narrower within, for the purpose of increasing the light; they are lower also inside than out, to the end that they may throw light on the frieze and cornice. Each window is enclosed between pilasters corresponding in height to the columns on the outside, so that there are thirty-six columns without and thirty-six pilasters within;[2] over the pilasters on the inside is the architrave,
